This invention relates in general to mortise latches and deals more particularly with a mortise latch of the type which has a case, a normally projected latch bolt, inner and outer hubs journalled within the case for independent coaxial rotation and means for retracting the latch bolt in response to rotation of either of the hubs in at least one direction relative to the case. Latches of the aforedescribed general type may be set-up for inner and outer knob or lever handle operation or combinations thereof. If a latch is arranged for two-directional knob operation, it is generally desirable that knob action be balanced, that is that both hubs offer substantially uniform resistance to operational torque in either direction. However, if either hub is to be arranged for lever handle operation some auxiliary spring means is usually required to compensate for the moment of the lever handle which results from its center of gravity being radially offset from its axis of rotation. Further, since a lever handle usually offers substantially greater mechanical advantage than a knob, it is generally desirable that a lever handle have somewhat greater resistance to operational torque than a knob to compensate for its greater mechanical advantage and to provide a desired degree of reactive response to manual operation.
Heretofore, it has been generally customary to provide auxiliary spring means associated with the lever handle assembly or more particularly with a rose or escutcheon which comprises a part of the assembly. However, such a special feature within the lever handle assembly adds substantially to its cost. Further, a lever handle assembly having such a special feature must generally be handed, all of which further significantly increases the cost of providing the desired latch functions. Accordingly, it is the general aim of this invention to provide a substantially universal mortise latch structure which may be readily adapted to either knob or lever handle operation during manufacture or in the field and at minimal expense.